Damping Of Inter-area Oscillations Research Articles

A Frequency-shaped Controller for Damping Inter-area Oscillations in Power Systems

This paper discusses how to design an inter-area oscillations damping controller using a frequency-shaped optimal output feedback control approach. This control approach was chosen because inter-area oscillations occur at a particular frequency range, from 0.2 to 1 Hz, which is the interval the control action must be prioritized. This paper shows that using only the filter for the system states can sufficiently damp the system modes. In addition, the paper shows that the filter for the input can be adjusted to provide primary frequency regulation to the system with no effect to the desired damping control action. Time domain simulations of a power system with a set of controllable power injection devices are presented to show the effectiveness of the designed controller.

Optimal siting, sizing, and parameter tuning of STATCOM and SSSC usingMPSO and remote coordination of the FACTS for oscillation damping of powersystems

In electromechanical oscillation damping within power system, power system stabilizers (PSSs) are often deployed. However, a PSS is less effective in damping interarea oscillation and is limited by changes in network configuration due to weak tie-lines and load variations. Consequently, this paper presents a wide-area coordination approach that damps interarea oscillations using FACTS devices and phasor measurement units. We selected a static synchronous compensator (STATCOM) and static series synchronous compensator (SSSC) for realistic power system interarea oscillation damping. The performance of the coordinated FACTS installed in a power system depends on their suitable locations, sizes, tuned parameters, and remote input signal selection. Hence, we formulated a multiobjective problem to provide the STATCOM and SSSC's optimal solutions using multiobjective particle swarm optimization. In addition, we employed a participation factor to select suitable generator speed deviations as the wide area stabilizing signal. The proposed approach was tested on different configurations of the Kundur $2$-area $4$-machine test system within MATLAB and Psat environments. The outcome of the nonlinear simulation proved that the multimachine power system stability was enhanced.

Damping of Inter-Area Oscillations via Modulation of Aggregated Loads

Low frequency electromechanical oscillations can pose a threat to the stability of power systems if not properly addressed. This paper proposes a novel methodology to damp these inter-area oscillations using loads, the demand side of the system. In the proposed methodology, loads are assigned to an aggregated cluster whose demand is modulated for oscillation damping. The load cluster control action is obtained from an optimal output feedback control (OOFC) strategy. The paper presents an extension to the regular OOFC formulation by imposing a constraint on the sum of the rows in the optimal gain matrix. This constraint is useful when the feedback signals are generator speeds. In this case, the sum of the rows of the optimal gain matrix is the droop gain of each load actuator. Time-domain simulations of a large-scale power system are used to demonstrate the efficacy of the proposed control algorithm. Two different cases are considered: a power imbalance and a line fault. The simulation results show that the proposed controllers successfully damp inter-area oscillations under different operating conditions and with different clustering for the events considered. In addition, the simulations illustrate the benefit of the proposed extension to the OOFC that enable load to provide a combination of droop control and small signal stability augmentation.

Coordinated design of PSS and unified power flow controller using the combination of CWT and Prony methods with the help of SPEA II multi‐objective optimisation algorithm

Since the initial objective of power system stabiliser (PSS) units and flexible AC transmission system (FACTS) devices is the damping of inter-area and local oscillations, it is very substantial that the network electromechanical oscillatory modes are identified for tuning the controller of large-scale interconnected power systems. In this research, a method based on the combination of continuous wavelet transform and Prony algorithm is presented to study low-frequency electromechanical oscillations of the power system. The coordinated design of PSS and FACTS parameters become a multi-objective optimisation problem that will be solved using the SPEA II. The residue method is used to improve damping and satisfy the controller constraints of the suggested power systems. Finally, the proposed method of mode estimation and controller design is simulated on the two well-known test case systems, namely IEEE 2-area 4-generator and New England- New York 68-bus 16-generator systems using MATLAB software. The results represent accurate performance and validity of the proposed method to improve oscillation damping, dynamic stability of the power systems.

Design Supplementary Controller Based on Stabilizing Effect of Delay for Damping Inter Area Oscillations in a Power System

Design Supplementary Controller Based on Stabilizing Effect of Delay for Damping Inter Area Oscillations in a Power System

Optimal Controller Design for Interconnected Power Networks With Predetermined Degree of Stability

A novel procedure for the design of an optimal controller with a predetermined degree of stability to enhance damping of interarea oscillations in interconnected power networks is presented in this paper. The proposed approach includes a feedback controller, which is independent of internal disturbances as a stabilizer. A tuning parameter is also provided, which treats load changes as disturbances. The gains of the proposed controller are calculated based on moving the dominant poles to the left on the S plane to obtain a desired stability margin and provide a prescribed degree of stability. In order to better validate the performance of the proposed controller, a multiarea power system is considered with different step load changes that are applied successively in simulations. The time responses and eigenvalue analysis are presented and discussed thoroughly. It is shown in the results that the developed optimal controller can effectively damp the frequency and tie-line power deviations in interconnected power systems.

Fast Frequency Response From Smart Induction Motor Variable Speed Drives

Using their fast power reduction capabilities, the induction motor variable speed drives can successfully participate in the power system primary frequency control. A new control strategy for fast frequency support from the diode front-end induction motor variable speed drive is presented in this paper. By this, practical restrictions are considered. In this context, an existing conventional scheme presented in literature is firstly modified by deploying an estimated motor's power losses for a more exactly control design. Next, a novel control scheme is proposed. It attains the fastest frequency support from the drive and simultaneously restricts its minimum power consumption to a given positive value to prevent regeneration mode during the frequency support process. The frequency of applied voltage to the motor is adjusted through a proportional-integrator compensator with deviation of the drive's consumption power from its reference power as input. The reference power is synthesized by permanent and temporary components, which are determined based on deviation and time derivative of the power system's frequency, respectively. The effectiveness of the proposed smart drive for the primary frequency control is investigated using the New England 39 bus and a more realistic Great Britain 36 zone test networks. It improves system frequency response in terms of the rate of change of frequency and the frequency nadir. Furthermore, the new control scheme can contribute to quickly damping inter-area oscillations in multi-machine power systems.

Power oscillations damping using wide-area-based solar plant considering adaptive time-delay compensation

The aim of this paper is to investigate the use of the ever increasing penetration of renewable energy into the power grid to solve challenging problems such as inter area power oscillations without the use of expensive power electronic devices and power system stabilizers. The increase in size of interconnected power systems, energy demand, and installation of remote renewable energies with relatively weak tie-lines has witnessed different stability problems such as low-frequency inter-area oscillations. Inter-area oscillation reduces system stability and transmission capacity. Without effective damping control mechanism, these oscillations could prolong and threaten the security of the system. This paper proposes a supplementary controller from a photovoltaic (PV) solar plant for damping inter-area oscillations. Due to its strong correlation to active power flow and monitoring system stress, area phase-angle difference is employed for the remote signal input of the controller. The signal can be obtained from phasor measurement unit (PMU) through wide-area measurements systems (WAMS). To deal with a wide range of variable delay in the signal input, an adaptive compensator is designed to reduce the impact of the communication latency using neuro-fuzzy inference system. A two-area four-machine test system is used and simulated with a Simulink-based package developed for the work of this study. The time-domain simulations, modal and frequency response analysis demonstrate the capability of the proposed controller to effectively damp inter-area oscillations, under a small- and large-scale disturbances and against a wide range of time delays.

Inter area Stability Enhancement of Interconnected power system using Second-order Sliding Mode Controller

The presence of DFIG (Doubly Fed Induction Generator) affecting the stability of the inter-area interconnected power system due to the lagging response of DFIG under undesirable conditions like faults. This paper addresses a Second-order Sliding Mode controller for DFIG to damp inter-area frequency oscillations of the interconnected power system. The proposed heuristic controller is a sliding mode controller of second-order type and works based on the reactive power capability of DFIG. This novel controller is not affected by system modeling uncertainties and unwanted parameter variations. The proposed controller is designed and implemented on 3-bus interconnected system in MATLAB/Simulink environment and the results obtained compared with the conventional controller under different fault conditions to show the effectiveness. Results demonstrated that the sliding mode controller effectively damping inter-area oscillations compared with a conventional controller.

FACTS Providing Grid Services: Applications and Testing

The role of flexible alternating current transmission systems (FACTSs) in the provision of grid services is becoming increasingly important, due to the massive integration of intermittent renewable energy sources, energy storage systems, and the decommissioning of thermal plants. A comprehensive literature review of grid services offered by FACTS is performed, focusing on the different grid services that they can provide, such as power flow control, reactive power control, voltage control, power quality improvement, harmonic mitigation, improvement of transient stability, and damping of inter-area and intra-area oscillations. These grid services need to be realistically and economically validated in suitable testing environments. A review of relevant standards, guides, and the literature is performed, which covers the entire range from functional specification and factory testing up to the field testing of FACTS. Advanced industry practices, such as controller hardware in the loop (CHIL) testing of FACTS controllers by the manufacturer, and recent trends, such as CHIL testing of replica controllers by the owner, are underlined. Limitations of conventional testing and CHIL testing are explained and the use of power hardware in the loop (PHIL) simulation for FACTS testing is discussed. CHIL and scaled-down PHIL tests on a transmission static synchronous compensator (STATCOM) are performed and a comparison of the results is presented.

Analysis and Design of a Wide-Area Damping Controller for Inter-Area Oscillation With Artificially Induced Time Delay

One of the major issues in an interconnected power system is the low damping of inter-area oscillations. A proportional-derivative (PD) compensator is a popular control method which is extensively being used as an active damping control in various domains such as robotics, smart structure, etc. However, existence of noise in wide-area signal makes an ideal PD compensator unrealisable in power systems. In this endeavour, a new methodology christened as time-delayed control is proposed where artificial delay is used to provide derivative action which acts as a damping component of wide-area controller. The delay margin is computed for the closed loop system using Razumikhin approach. It is observed that the proposed controller is able to damp the oscillations adequately with reduced sensitivity to the noise in the signals. Further, the proposed controller is able to provide robustness against uncertainties arising from the system dynamics and inherent delay in communication channel.

A delay-dependent anti-windup compensator for wide-area power systems with time-varying delays and actuator saturation

In this paper, a delay-dependent anti-windup compensator is designed for wide-area power systems to enhance the damping of inter-area low-frequency oscillations in the presence of time-varying delays and actuator saturation using an indirect approach. In this approach, first, a conventional wide-area damping controller is designed by using H&#x221E output feedback with regional pole placement approach without considering time-varying delays and actuator saturation. Then to mitigate the effect of both time-varying delays and actuator saturation, an add-on delay-dependent anti-windup compensator is designed. Based on generalized sector conditions, less conservative delay-dependent sufficient conditions are derived in the form of a linear matrix inequality &#x0028 LMI &#x0029 to guarantee the asymptotic stability of the closed-loop system in the presence of time-varying delays and actuator saturation by using Lyapunov-Krasovskii functional and Jensen integral inequality. Based on sufficient conditions, the LMI-based optimization problem is formulated and solved to obtain the compensator gain which maximizes the estimation of the region of attraction and minimizes the upper bound of L2-gain. Nonlinear simulations are performed first using MATLAB &#x002F Simulink on a two-area four-machine power system to evaluate the performance of the proposed controller for two operating conditions, e.g., 3-phase to ground fault and generator 1 terminal voltage variation. Then the proposed controller is implemented in real-time on an OPAL-RT digital simulator. From the results obtained it is verified that the proposed controller provides sufficient damping to the inter-area oscillations in the presence of time-varying delays and actuator saturation and maximizes the estimation of the region of attraction.

VSC-MTDC Operation Adjustments for Damping Inter-Area Oscillations

Application of voltage source converter based multi-terminal high-voltage direct current (VSC-MTDC) grids operation adjustment for damping inter-area oscillations are addressed and analyzed in this paper. The new operation adjustment method is proposed to meet short-term solution requirements and accommodate critical operation conditions where the conventional damping stabilizer by using active power modulation cannot provide sufficient damping. Based on the sensitivities with respect to the active power injections of VSCs and the interior point algorithm, an operation optimization method is presented to obtain a proper VSC-MTDC operation scheme to achieve better damping performance for an ac/VSC-MTDC system. For some critical operation conditions in which an inter-area oscillation has been detected, an operation rescheduling method is proposed as an emergency oscillation control. Time-domain simulations are performed on a New England system with a five-terminal MTDC grid. A comparative study with a conventional damping stabilizer is also included in the case study. Both the theoretical analysis and the time-domain simulations have verified the effectiveness and superiority of the two proposed methods.

Anti‐windup compensator design for power system subjected to time‐delay and actuator saturation

In this study, a delay-dependent anti-windup compensator (AWC) is designed for supplementary damping control (SDC) of flexible AC transmission system (FACTS) device to enhance the damping of inter-area oscillations of the power system subjected to time-delay and actuator saturation. By employing global signal measurements, an SDC of FACTS device is designed without considering the effect of time-delay and actuator saturation to stabilise the power system using a robust output feedback controller with pole placement approach. Then, based on the generalised sector condition and Lyapunov–Krasovskii functional, an add-on delay-dependent AWC is designed to mitigate the adverse effect of time-delay and actuator saturation non-linearity. For the design of delay-dependent AWC, sufficient conditions guarantee the asymptotic stability of the closed-loop power system are formulated in the form of linear matrix inequalities (LMIs). These conditions are cast into the LMI-based convex optimisation problem to compute the AWC gains. To evaluate the effectiveness of the proposed controller, non-linear simulations were performed first using MATLAB/Simulink. Then, the authors implemented the proposed controller in real-time using the Opal-RT digital simulator. From the obtained results, it is observed that the proposed controller enhances the damping of inter-area oscillations by compensating the effect of time delay and actuator saturation.

Cooperative Control for Damping Inter-Area Oscillations Using Dynamic State Information

With the ever-growing complexity of a modern power system, decentralized control is becoming a more advantageous framework for maintaining its stable operation. Recently, some research work has been done on decentralized control for mitigating inter-area oscillations based on dynamic state estimation. This paper illustrates that in the decentralized control scheme, the use of dynamic state estimation can compromise controller performance and decrease the damping of inter-area oscillations. To address this problem, this paper proposes a cooperative-based supplementary excitation control strategy for damping inter-area oscillations using dynamic state information. By eigenvalue analysis, this paper reveals the relationship between the estimator's parameter and inter-area modes. Furthermore, communication is utilized in the proposed controller to neutralize the adverse impact of using dynamic state estimation on damping performance. The connection between the communication structure and inter-area modes is also analytically given. Finally, the well-known New England test system with 10 generators and 39 buses is employed to demonstrate the analytical results.

ANN Controller for Inter-area Oscillations Using Deep Learning in Power Systems

If the Low-frequency oscillations including Local and Inter-area Mode in power systems are not properly damped out, they can cause critical effects, including wide-area outage. In order to damp out these oscillations, the PSS (Power System Stabilizer) of each synchronous generator is typically used. This, however, cannot damp out inter-area oscillations. Although research on damping inter-area oscillations is conducted to resolve the mentioned problems, the Lead Lag Controller for damping the oscillations used in FACTS (Flexible AC Transmission System) devices including VSC (Voltage Source Converter) has limitations in that it is a linear controller designed at a linearized Power System models so there are some limitations incurred by the variable and unpredictable power system states, so that fixed controller parameters cannot properly damp out these oscillations. Meanwhile, the AI (Artificial Intelligence) techniques including supervised learning, unsupervised learning, and reinforcement learning are applied in various engineering fields to overcome a lot of nonlinear problems like those of power systems. In this paper, the ANN (Artificial Neural Network) controller, a kind of AI controller, was used to damp out inter-area oscillation at different power system operating conditions, after which the results were analyzed.

Investigations of Large-Scale Voltage-Dependent Loads for Damping Inter-Area Oscillations: Mechanism and Robust Decentralized Control

To uncover the mechanism by which voltage-dependent loads (VDLs) influence electromechanical dynamics, this paper mathematically deduces the damping torque induced by VDLs based on a single machine infinite bus system. Moreover, by continuously regulating the terminal voltage of a typical large-scale VDL, i.e., the aluminum electrolysis load, this paper proposes a novel load damping control architecture to dynamically modulate the power consumption of controlled loads so as to eliminate interarea oscillations in power systems. Specifically, the decentralized load damping controllers (LDCs) used in this architecture are designed by a proposed multistage mixed ${{{H}}_{2}} / {{{H}}_\infty }$ control approach to guarantee robustness against uncertainties (e.g., tie-line outages and wind generation fluctuations) as well as to ensure reasonable control efforts of controlled VDLs. Simulation results on the modified New England and New York interconnected system validate the method for analysis of VDLs’ effects on interarea oscillations and show the proposed load damping control strategy can satisfactorily damp interarea oscillations over multiple operating points.

Damping Inter-Area Oscillations by Coordination of 3PSS and UPFC Using PSO

Power System Stabilizer (PSS) is one of the most used controllers in the local generations, primarily it aimed to suppress local mode of oscillations. On the other hand, the Unified Power Flow Controllers (UPFC) the most versatile member of flexible alternating current transmission system devices to simultaneously control real and reactive power flows on transmission lines, as well as regulate selected bus voltage. Each of these controllers, on their own, can show satisfactory performance to enhance power system stability. However, when they utilized together, their dynamic performance can degrade due to controller interaction, that should be strategically optimized. In this paper, the coordinated design of pss's and upfc is realized to damp inter-area oscillations in two-area power system using particle swarm optimization (PSO) method. The simulated cases in Matlab environment show that the interaction of pss's and upfc can be optimized, so the inter-area oscillations can be effectively mitigated following after fault, the simulation results of the uncoordinated design are also presented.

Robust wide-area TCSC controller for damping enhancement of inter-area oscillations in an interconnected power system with actuator saturation

Actuator saturation is an inevitable phenomenon in control system which degrades the system performance if it is not considered in the controller design. In this paper, a robust wide-area damping controller is designed for a thyristor controlled series capacitor (TCSC) to enhance the damping of inter-area oscillations when the power system is subjected to actuator saturation. A generalized sector condition is used to represent the nonlinear effects introduced by the actuator saturation in the closed-loop system. By using these conditions, the stabilization conditions for ensuring asymptotic stability of the closed-loop system are derived based on an quadratic Lyapunov criterion. The design of damping controller that maximizes the region of attraction is formulated in the form of linear matrix inequality (LMI) and solved as an optimization problem to achieve damping of inter-area oscillations. In addition to the damping controller, further, a robust pole placement approach is employed to place the closed-loop poles in a prescribed stability region. Two case studies, namely, a two-area four-machine power system and 16 machine 68 bus power system are considered to evaluate the performance of the proposed damping controller.

Nonlinear model predictive control of HVDC for inter-area oscillation damping

This paper presents a nonlinear model predictive control (NMPC) strategy for high-voltage direct current (HVDC) transmission to damp inter-area oscillations in the power grid. An ensemble Kalman filter (EnKF) method is implemented to generate nonlinear model-based future predictions within a finite horizon. Unlike existing control methods that are based on approximate linearization of a system, the NMPC-EnKF approach maintains full nonlinearity in the AC-HVDC system by introducing ensembles to represent and propagate the distribution of states and errors. The proposed approach is tested on both a modified two-area, four-machine system and a modified IEEE New England system. Both small- and large-signal-disturbance stability studies are tested to validate the performance of the proposed approach. Extensive results show the effectiveness of the NMPC-EnKF approach for damping inter-area oscillations.